Production of an Anise- and Woodruff-like Aroma by Monokaryotic Strains of Pleurotus sapidus Grown on Citrus Side Streams

Abstract

The production of natural flavors by means of microorganisms is of great interest for the food and flavor industry, and by-products of the agro-industry are particularly suitable as substrates. In the present study, Citrus side streams were fermented using monokaryotic strains of the fungus Pleurotus sapidus. Some of the cultures exhibited a pleasant smell, reminiscent of woodruff and anise, as well as herbaceous notes. To evaluate the composition of the overall aroma, liquid/liquid extracts of submerged cultures of a selected monokaryon were prepared, and the volatiles were isolated via solvent-assisted flavor evaporation. Aroma extract dilution analyses revealed p-anisaldehyde (sweetish, anisic- and woodruff-like) with a flavor dilution factor of 218 as a character impact compound. The coconut-like, herbaceous, and sweetish smelling acyloin identified as (2S)-hydroxy-1-(4-methoxyphenyl)-1-propanone also contributed to the overall aroma and was described as an aroma-active substance with an odor threshold in air of 0.2 ng L−1 to 2.4 ng L−1 for the first time. Supplementation of the culture medium with isotopically substituted l-tyrosine elucidated this phenolic amino acid as precursor of p-anisaldehyde as well as of (2S)-hydroxy-1-(4-methoxyphenyl)-1-propanone. Chiral analysis via HPLC revealed an enantiomeric excess of 97% for the isolated product produced by P. sapidus.

A Novel O- and S-Methyltransferase from Pleurotus sapidus Is Involved in Flavor Formation

“…20 In a recent study, P. sapidus produced up to 160 mg p-anisaldehyde per liter of culture medium, and further supplementation studies using labeled tyrosine revealed the formation of labeled panisaldehyde. 21 Thus, an analogous biosynthetic pathway compared to B. adusta and the presence of an OMT in the biosynthesis of p-anisaldehyde in P. sapidus seemed evident. However, enzymes involved in potential methylation reactions catalyzing the formation of p-anisaldehyde are so far unknown.…”

Improved Foods Using Enzymes from Basidiomycetes

“…While the potential of basidiomycetes for the production of volatile flavours is clearly far from being fully exploited, solid-state [115] and submerged cultures [116] were shown to provide suitable experimental systems to valorise renewable biomass from food processing, such as pomace, molasses, leaves or peels. This allows the use of non-food biomass as a cheap source of nutrients and, at the same time, provides a sink for these large volume side-streams.…”

Special Issue “Selected Papers from the 16th Weurman Flavour Research Symposium”

“…Bürger et al [ 3 ] investigated the production of an anise- and woodruff-like aroma using monokaryotic strains of Pleurotus sapidus grown on citrus side streams. Their main conclusions highlighted the role of the character impact compound p -anisaldehyde in the anise- and woodruff-like note while the acyloin identified as (2S)-hydroxy-1-(4-methoxyphenyl)-1-propanone also contributed to the overall aroma.…”